Fumigant composition containing propargyl bromide and methyl bromide



3,009,853 FUMIGANT CGWUSITION CQNTAINHIG PRO- PARGYL BROMEE AND METHYLBRQMIDE Charles R. Youngson, Long Beach, and Cleve A. I. Goring, GardenGrove, Calif., assignors to The Dow Chemical Company, Midland, Mich, acorporation of Eelaware r No Drawing. Filed Oct. 30, 1959, Ser. No.849,7o5 9 Claims. ((1. 167-22) The present invention relates to fumigantcompositions and is particularly concerned with a new furnigantcomposition and an agronomic practice for improving the ability of soilto support plant growth.

It is an object of the present invention to provide a new fumigantcomposition. A further object is to supply a new agronomic practice andcomposition for improvi ing the plant growing properties of soil and theability The new fumigant composition of the present invention comprisesabout one part by weight of propargyl bromide in admixture with fromabout 0.3 to 9 parts by weight of methyl bromide. While this compositionad vantageously may be employed in many types of fumigation operations,it conveniently adapts itself to the treatment of soil or other growthmedia to improve the ability of the soil to support plant growth and tobenefit the plants grown in the treated soil. Such practice protects theplants from the ravages of soil-dwelling invertebrate organisms whichattack their roots and improves the growth and harvest of crop plants.It has also been found that the treatment accomplished changes in thesoil which stimulate the growth and improve the growth characteristicsof crops growntherein. It is among the advantages of the presentinvention that the toxicants in the mixture appear to be mutuallyactivating so that a greater than additive, or synergistic, result isaccomplished as regards the effect on the plant growing properties ofthe soil and a control of insect and other undesirable organisms andparticularly invertebrates such as wire worms and nematodes.

The composition comprising the mixture of toxicants is sufficientlyincreased in effectiveness so as to permit the eiiective utilization ofreduced amounts of propargyl bromide and of methyl bromide on soil andthe obtaining of crop yields and controls of soil-dwelling organismswhich are much superior to those obtained when either of theconstituents of the mixture is employed alone. An additional advantageis that these reduced effective dosages of the mixture of toxicantsmaterially reduce the hazards of soil residues. Thus, the practice ofthe present invention provides a very desirable economic advantage forthe agriculturalist.

Propargyl bromide is a mobile liquid which boils at 88-90 C. atatmospheric pressure and methyl bromide is an easily liquefied gas whichboils at 4.5 C. at atmospheric pressure. Mixtures of the compounds aresomewhat soluble in many organic solvents and of low solubility in waterand are adapted to be readily and conveniently distributed in soil. Itis among the advantages Patented Nov. 21,, 1961 of the present inventionthat mixtures of these compounds, while sufficiently persistent toaccomplish the desired effect upon the soil and upon the soil inhabitingorganisms, dissipate in a reasonable period of time. Still anotheradvantage is that mixtures of these compounds permeate soil for adistance of several inches from the point of application depending uponthe temperature, organic content, moisture content, compactness andphysical consistency of the soil or growth media.

In carrying out the improved agricultural practice of the invention, thepropargyl bromide and methyl bromide may be mixed together and suchmixtures employed directly in parasiticidal dosages for the treatment ofsoil. However, the present invention also embraces the employ- I" mentof gaseous, liquid or dust compositions containing the mixture oftoxicants and for any fumigant purpose where the composition is useful.Thus, the mixture of toxicants may be dissolved in a suitable liquidcarrier to provide compositions adapted to be distributed in soil. Suchliquid compositions may also be employed to fumigate the surfaces ofcertain fruits, vegetables and grains where these products tolerate thefumigation action. Similarly, the propargyl bromide and methyl bromidemay be dispersed on or in a granular or finely divided solid carrier toprovide compositions adapted to be distributed in soil or employed asconcentrates and subsequently diluted with additional inert carrier toproduce the ultimate treating compositions. In a further mode of opera:tion, the propargyl bromide and methyl bromide may be blended with asuitable surface-active dispersing agent with or without one or moreliquid carriers to provide concentrates suitable for dispersion in waterto prepare soil treating compositions in the form of aqueous dispersionsor emulsions.

The compositions of the invention may be prepared in any suitablefashion. Since propargyl bromide and methyl bromide are miscible in allproportions, compositions without carriers may be prepared by simplemixing of the components at convenient temperatures. In the preparationof compositions containing a liquid organic carrier, propargyl bromideand methyl bromide are thoroughly mixed in the liquid organic carrier atconvenient temperatures. Suitable organic carriers include liquidaliphatic and aromatic hydrocarbons such as toluene, xylenes, naphthasand hydrocarbon mixtures derived from the distillation of petroleum orcoal, and other organic solvents such as acetone. For some fumigationoperations such carriers as carbon tetrachloride or ethylene dichloridemay be employed. In general, it is preferred to avoid liquid carriershaving such low flash points as to constitute a fire hazard or such highboiling points as to leave undesired residues after use of thecompositions. Depending upon the concentration of the mixture oftoxicants, such aug mented compositions are adapted to be distributed inthe soil or otherwise, or employed as concentrates and subsequentlydiluted with additional carrier to produce the ultimate treatingcompositions.

In a preferred embodiment of the invention, selected petroleumdistillates are employed as liquid carriers. Petroleum distillates usedin such embodiments are carefully fractioned portions boiling almostentirely under 400 F. at atmospheric pressure and having a flash pointabove about F. These fumigant compositions are characterized byexcellent penetrating properties and by low fire hazard to the shipperand user.

In preparing dispersible concentrate compositions, propargyl bromide andmethyl bromide are mixed in the proportions previously set forthtogether with a surface-active dispersing agent soluble in thecomposition with or without the further addition of a liquid organiccarrier. The surface-active agents are usually employed in the amountfrom about 1 to about 20 percent by weight of the combined weight of thetoxicant mixture and surface-active agent. Suitable surface-activedispersing agents include polyoxyalkylene derivatives of alcohols,phenols and organic acids; oil-soluble petroleum sulfonates;polyoxyethylene derivatives of glycerol and glycols; and the like.

In compositions in which propargyl bromide and methyl bromide aredispersed on or in a granulated or finely divided solid carrier, thecomponents may be added directly to the solid carrier with mechanicalmixing. Alternatively, the components may be combined with one or moreof the aforementioned liquid organic carriers and the resultingcompositions admixed with the solid carrier. Suitable solid carriersinclude silica gel, wood flour, fullers earth, chalk, gypsum and thelike.

In formulating the compositions, it is essential to maintain proportionsfrom about one part by weight of propargyl bromide to about 0.3 to 9parts by weight of methyl bromide and to provide an efiective amount ofsaid mixture in the finished composition in order to obtain the desiredsynergistic elfect. The concentration of the mixture of toxicants inorganic solvent compositions employed to supply the desired dosage isgenerally from about 10 to about 85 percent by weight. With aqueouscompositions, the required dosage is generally supplied withcompositions containing from about 1 to about 50 percent, althoughconcentrations of 0.0002 percent by weight may be conveniently employedin irrigation treatments of soil. In compositions wherein the activemixture is dispersed on a solid carrier, it is generally desirable toemploy from about 1 to about 30 percent by weight of the above mixtureof active ingredients in the finished solid composition. With highcapacity carriers, such as silica gel, the active ingredients may amountto 50 percent by weight or more of the solid composition. In any case,it is desirable to employ suflicient of the solid carrier so that theliquid composition is sorbed to provide a free-flowing solid mixture. Incompositions to be employed as concentrates, the toxicant mixtureoftentimes is present in a concentration from about to about 95 percentby weight.

The soil may be treated with the toxicant mixture or a compositioncontaining the mixture of toxicants in any suitable fashion. With liquidcompositions, good results have been obtained by depositing the activefumigant mixture at regular intervals beneath the surface of the soil.Such deposition may be accomplished readily by automatic machinery or byhand-operated apparatus. Thus, the active composition may be sprayed orotherwise deposited in a furrow which is subsequently closed to keep theactive agents in the desired zone of the soil to be treated.Alternatively, the liquid compositions may be injected into the soil atpredetermined intervals. In any case, the active composition is usuallydeposited at a depth from about 4 to about '18 inches below the soilsurface.

In row treatments it is advantageous to place the fumigant compositionat least 12 inches below the surface of the seed bed and to seal in thefumigant by listing the soil or by other suitable means such as ringrollers or press sealers attached behind the applicator. In overallapplications with chisel-type applicators, the fumigant composition maybe applied in uniform treatments 1 to 12 inches apart at a depth of 6 to8 inches. With plowsole applications, it is desirable to employ about 8inches spacing between the furrows and to spray or otherwise introducethe fumigant composition so as to cover the bottom of the furrow. Whereinjection of the active composition at intervals is employed, goodresults are obtained when injecting at intervals from 3 to about 12inches, although somewhat greater intervals may be em- 4!, ployed incertain cases. In the above operations, it is desirable to apply thefumigant composition after the soil has been worked into seed bedcondition and when the soil temperature is above 50 F. and the soilmoisture content is suflicient for seed germination.

In another mode of operation, the fumigant composition in emulsifiahleform may be dispersed in water employed to irrigate the soil. In thismethod, the amount of water may be varied in accordance with theporosity and water-holding capacity of the soil in order to obtain thedesired depth of distribution of the toxicant mixture.

The amounts of the propargyl bromide and methyl bromide composition tobe employed will vary depending upon such factors as the type andcondition of the soil, the varieties and growth stages of soil pests tobe controlled and the particular crop to be planted thereafter. Theessential criterion is to employ an amount for accomplishing the desiredeffect upon the soil-dwelling invertebrate organisms and the plantgrowing properties of the soil. In general, good results are obtainedwhen the mixture of to-xicants is distributed in growth media to a depthof from 4 to 12 inches at a dosage of at least one pound per acre. Infield applications, the mixture of toxicants is usually introduced intothe soil at a depth of about 6 inches and at a dosage of from 1 to 50pounds per acre. Where compositions embodying a liquid or solid carrierare used, the amount of composition is adjusted to distributesubstantially the above described amounts of the active toxicant mixtureper acre. The required amount of the toxicant mixture in the soil mayconveniently be supplied per acre treated in from about 10 to gallons oforganic solvent carrier, in from 10 to 162,000 gallons or more of theaqueous carrier or in from about 50 to 1,000 pounds or more of the solidcarrier.

In one embodiment of the invention, the treated soil is planted with thedesired crop plant following the distribution of the toxicant compoundsin the soil. Where minimum dosages of the toxicant compounds aredistributed in soil, the treated soil may be immediately planted withthe desired crop. Following the distribution of larger dosages of thetoxicant compounds, it is desirable that any planting operation not becarried out for a. period of from several hours to several days, theexact period depending upon the concentration of the toxicant compoundsin the soil and the resistance of the species concerned to thecompounds. Where the mixture of toxicant compounds is employed for thetreatment of the soil adjacent to the root system of established plantshaving resistance to the compounds and in side dressing operations, theexisting vegetation is not unfavorably effected by minimum effectiveconcentrations of the toxicant compounds temporarily present in thesoil.

Illustratively, beneficial results were obtained by injecting acetonesolutions of the active fumigauts of the present invention into sandyloam soil naturally infested with root-knot nematodes.

Specifically, acetone solutions of propargyl bromide and methyl bromidewere prepared at concentrations sufficient to provide desired dosages inpounds per acre foot by application of 0.1 milliliter of said solutionto grams of soil. The infested sandy loam soil was placed in 4 ouncescalable jars and thereafter treated with the foregoing solutions byinjection. The jars of treated soil were then sealed and set aside atabout 70 F. for one week.

Following the one week interval, the containers were unsealed and thesoil allowed to aerate for one week and thereafter planted with threecucumber seeds. During the subsequent growing period, no adverse effectattributable to the presence of residual fumigant on the growth of theseedlings was observed. After the cucumbers had been allowed to grow fora sufiicient period that root-knot nematode galls were developed in thevarious containers, the

cucumber roots were washed, inspected for gall formation, and noted inthe following manner:

TABLE I Toxicity of fumigants to root-knot nematodes Pounds peracre-foot Percent Samples control of Methyl Propargyl nematodes bromidebromide TABLE II Toxicity of combinations of methyl bromide andpropargyl bromide fumigants t root-knot nematodes Combination Pounds peracre-foot Percent control proportions of nematodes Methyl PropargylMethyl Propargyl Actual Expected bromide bromide bromide bromideAdditionally, compositions of the fumigants containing about 1 part byweight of propargyl bromide and from about 0.3 to about 9 parts byweight of methyl bromide were admixed with the following adjuvants: (1)finely divided inert solids, such as silica gel and the like; (2)emulsifying and dispersing agents such as dimeric alkylated arylpolyether alcohols, alkyl aryl sulfonates and the like; and (3) lowboiling petroleum hydrocarbon distillates, such as Stoddard solvent,Standard Thinner 250, and the like. The amount of such adjuvantsemployed in these compositions may vary from 50 to 99 weight percent ofthe finely divided inert solids, from 1 to 20 weight percent of theemulsifying and dispersing agents and from 15 to '90 weight percent ofthe petroleum distillates. The compositions obtained with the petroleumdistillates had at least a flash point greater than 100 F., and containabout 15 weight percent of the fumigants.

The concentrate compositions as above described are adapted to bedispersed in water to produce aqueous compositions having very desirablewetting and penetrating properties. The latter aqueous compositions andthe above described solvent fumigant compositions are adapted to beemployed to treat soil and to distribute the mixture of toxicantstherein in effective concentrations.

Use of such fumigant compositions gives results comparable to thosetabulated above.

The compositions of the present invention as hereinbefore described aredispersed in water to produce a material containing about 20 pounds ofthe respective toxicants per 200 gallons of ultimate material. Thedispersion, while under agitation is metered into irrigation water atthe pump outlet at the rate of 2 gallons per 1,000 gallons of irrigationwater. The water is in a state of turbulent flow as it comes from thepump which provides for the thorough mixing of the toxicants therein.About 2 acre inches of irrigation water is applied per acre to landheavily infested with wire worms and root-knot nematodes to accomplish awetting of the soil to a depth of about 12 inches. Two weeks after thetreatment, the soil is planted. In a check operation, adjacent butsimilarly infested soil is also planted. Eight weeks after seeding, theplots are inspected and representative plants lifted from the soil andtheir roots examined for evidence of wire worm and nematode attack. Theexamination indicates a commercial control of both soil organisms in thetreated soil, with severe infestation in the check plots.

The foregoing examples are included to illustrate the invention, and arenot to be construed as limiting it thereto. Various modifications can bemade in the present invention without departing from the spirit or scopethereof for it is understood that we limit ourselves only as defined inthe appended claims.

We claim:

1. A fumigant composition comprising, as active toxic ingredients, fromabout 1 part by weight of propargyl bromide and from about 0.3 to 9parts by weight of methyl bromide, the active toxic ingredients of saidcomposition being mutually activating.

2. A fumigant composition comprising a carrier and dispersed therein asactive toxic ingredients from about 1 part by weight of propargylbromide and from about 0.3 to 9 parts by weight of methyl bromide, theactive toxic ingredients of said composition being mutually activating,

3. A composition comprising, as active toxic ingredients, from about 1part by weight of propargyl bromide and from about 0.3 to 9 parts byweight of methyl bromide in intimate admixture with an inert carrier.

4. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a finely divided inert solid.

5. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a petroleum distillate.

6. A composition claimed in claim 3 wherein the active toxic ingredientsare admixed with a surface-active dispersing agent.

7. A fumigant composition which comprises an aqueous dispersion of thecomposition claimed in claim 3, wherein the active toxic ingredients areadmixed with a surface-active dispersing agent, and, said active toxicingredients being present in the amount of at least 0.0002 percent byweight.

8. In the practice of agricultural economy, the method which comprisesimpregnating soil with a parasiticidal dosage of a compositioncomprising from about 1 part by weight of propargyl bromide and fromabout 0.3 to 9 parts by weight of methyl bromide.

9. In the practice of agricultural economy, the process which comprisestreating soil with a parasiticidal dosage of a composition comprising asactive toxic ingredients from about 1 part by weight of propargylbromide and from about 0.3 to 9 parts by weight of methyl bromide inintimate admixture with a petroleum distillate.

References Cited in the file of this patent UNITED STATES PATENTS

8. IN THE PRACTICE OF AGRICULTURAL ECONOMY, THE METHOD WHICH COMPRISESIMPREGNATING SOIL WITH A PARASITICIDAL DOSAGE OF A COMPOSITIONCOMPRISING FROM ABOUT 1 PART BY WEIGHT OF PROPARGYL BROMIDE AND FROMABOUT 0.3 TO 9 PARTS BY WEIGHT OF METHYL BROMIDE.